It is well known that alkoxy radical-containing silicone resins can be used widely as the feed material in making electrical insulating materials, heat-resistant paints, protective coating materials, and copolymers with organic polymers. In the conventional scheme, as described in U.S. Pat. No. 3,389,114, the alkoxy radical-containing silicone resins are manufactured by hydrolysis of an alkoxy radical-containing organosilane. However, this method has three serious problems. First of all, in this method, as an alkoxy radical is hydrolyzed and polycondensation is performed, the molecular weight always increases in the reaction. Consequently, it is very difficult to achieve control of the molecular weight. Second, as the molecular weight distribution of the manufactured silicone resin is wide, the softening point and other responses to thermal variation become slow. Third, as all of the feed materials used depend on alkoxysilanes, the inexpensive chlorosilanes and cyclic siloxanes cannot be used resulting in increased costs.
Although there is another method for the manufacture alkoxy radical-containing silicone resins, described in Japanese Kokai Patent Application No. Sho 50[1975]-77500, which comprises the hydrolysis/polycondensation of a chlorosilane in water and alcohol it can only solve the aforementioned third problem, while it has no effect in solving the aforementioned first and second problems.
It is an object of this invention to provide a method for manufacturing alkoxy radical-containing silicone resins wherein the molecular weight, viscosity, thermal transition point, and alkoxy radical content can be easily controlled.